The present invention relates to a method of directly producing metallic uranium as a lump by reducing uranium dioxide.
It is known in the art that metallic uranium can be produced by reducing uranium dioxide with metallic calcium according to the following reaction: EQU UO.sub.2 +2Ca.fwdarw.U+CaO
[see "Nuclear Chemical Engineering, Second Edition" pp. 274 -279, by M. Benedict, T. H. Pigford et al. (1981, published by McGrow Hill Book Company)]
However, the melting point of a slag (CaO) as a reaction product is as high as 2572.degree. C., so that it is impossible to separate metallic uranium from the slag by melting and hence metallic uranium can be obtained only in the form of granules scattered in the slag. Accordingly, the metallic uranium granules must be separated out of the slag and the yield of purified metallic uranium is generally about 35 to 40%. Further, there is a drawback that the metallic uranium thus separated is susceptible to oxidation and is difficult to handle because it is granular.
Moreover, it is known to add calcium chloride in the above-described reaction in which uranium dioxide is reduced with metallic calcium [see "The Chemistry of Uranium", pp. 122-132, by J. J. Katz and E. Rabinowich (1951, published by Constable & Co., Ltd.)]. The addition of calcium chloride facilitates the reduction reaction, but the formation of granulated metallic uranium scattered in the slag and hence the recovery of granulated metallic uranium are inevitable.